Add block generator logic.

Now we are able to generate new blocks with yeoman.

generators/block/templates/src/styles/template.scss

@@ -0,0 +1,40 @@
+/**
+ * Use "rem" instead of pixels. 1rem = 16pixels
+ *    No need to use rem in situations of "1px". (usually used for borders width).
+ *
+ * Use BEM naming system for class names: http://getbem.com/naming/
+ *
+ * Use Mobile First approach.
+ *    Start with mobile device styling and then focus on other screen sizes by using @media (min-width: ...px).
+ *
+ */
+
+.<%= blockClassName %> {
+
+  &__header {
+    // Header Mobile.
+
+    @media (min-width: 1024px) {
+      // Header Desktop.
+    }
+
+    &-heading {
+      // Child Element.
+    }
+  }
+
+  &__visual {
+    &-image {
+      // Example of BEM usage.
+    }
+  }
+
+  &__content {
+
+  }
+
+  &__footer {
+
+  }
+
+}